The calibration factor should actually cause an integer array to be converted to a float array. Otherwise the rounding error is potentially too large to result in any meaningful plots. The imaging module is a giant mess in any case...the conversion to float should likely be happen fairly early on (on a copy of the data of course). As a short time fix you could also just replace the line by something akin to this:

```python
trace.data = np.require(trace.data, "float64") * calib
````